The present invention relates to a microscope eyepiece or ocular, especially designed to facilitate the use of the microscope in measuring lengths and angles.
Length and angle measurements by means of a microscope are made, for example, upon the matching or toric contact lenses. In modern soft contact lenses, the correction of astigmatism is accomplished by a toric outer surface whose axis must be in a definite predetermined relationship to what is called the DS axis. This DS axis extends through the two thickest edge points of the lens and the optical geometric center point of the contact lens. The inclination of the axis passing through the toric surface with respect to the DS axis is determined by the matching process.
It is known in the art to measure the inclination of the principal axes of a contact lens by means of a slit lamp. For doing this, a pointer is arranged on the outer side of a measuring eyepiece, in such position that it represents a continuation of the datum line of the eyepiece. Using this pointer, the inclination of the axis on the contact lens can be measured with reference to a graduated scale on a plate which is rigidly connected with the slit lamp, according to what is called the TABO system.
This known system of inclination measurement or angular measurement leaves much to be desired with respect to the precision or accuracy which is attainable. Furthermore, it is fatiguing and time-consuming for the lens matcher, since his direction of view must be continuously changed. Nevertheless, the use of the TABO system for angle measurements has gained general acceptance in the field since its introduction by the technical committee known as the "Technischen Ausschuss fur Brillen-Optik," from the initial letters of which the designation TABO is derived. According to this system, reading is effected from the right in counterclockwise direction for both eyes.
An object of the present invention is to provide a device to enable angle measurements to be obtained more conveniently and with greater accuracy than is possible with the prior art devices.
Another object is the provision of such a device in a simple, compact, and inexpensive form.